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i • 3 0 HISTORICAL AND 2005 SITE ASSESSMENT ACTIVITIES Assessment of petroleum hydrocarbon impact was initiated in August 1991 by consultants representing Exxon Prior to the September 2005 investigation, all site characterization activities were completed on behalf of Exxon The following is a summary of environmental assessment activities conducted to date This summary was prepared using information available in SJCEHD files for the site Locations of all soil borings and wells are included on Figure 2 Historical information regarding soil boring depths and well construction details are summarized in Table 1 Based on the extent of information available to Stratus personnel at the time this report was prepared, it appears that all site characterization activities described below were completed under the direction of Delta Environmental Consultants, Inc (Delta), with the exception of soil borings B-1 through B-10, which were implemented by Alton Geoscience, Inc (Alton) 31 Summary of Environmental Investigations ® Monitoring wells MW-1 through MW-3 were installed in August 1991 o Soil borings B-1 through B-10 were advanced in December 1991 a Monitoring wells MW-4 through MW-6 were completed in February 1992 o Monitoring wells MW-7 and MW-8 were constructed in March 1994 o Compliance soil sampling was completed in March 1994 at the time of UST and product line removal activities o Vapor extraction wells VEW-1 and VEW-2 were installed, and borings SB-1 through SB-3 were advanced, in January 1995 o Compliance soil and groundwater sampling was completed in December 1995, at the time that the new UST cavity was excavated Well VEW-2 was properly destroyed during the excavation Well VEW-3 was installed in May 1997 o Soil borings SB-4 through SB-9 were advanced, and monitoring wells MW-9 and MW-10 were constructed, in May 1999 3.2 2005 Site Characterization Activities The objectives of the site assessment activities were to o Further characterize the lateral and vertical extent of petroleum hydrocarbon impact to soil and groundwater o Additionally characterize the geology beneath the site To accomplish these objectives, Stratus implemented the following work activities o Advanced seven (7) CPT borings (CPT-1 through CPT-7) to depths ranging from approximately 80 to 100 feet bgs K\USA Gasolme\0835\Reparts\usa835-scm-assessment report doc Page 5 57RATU5